Investigations Into Failure Mechanism of Cascode GaN HEMTs Under Single Pulse Surge Current Stress

When Cascode gallium nitride (GaN) high-electron-mobility transistors (HEMTs) operate in the third quadrant, the surge current capability becomes one of the key parameters for practical applications. In this article, the failure behavior and mechanism of a 650 V Cascode GaN HEMT under single-pulse surge current stress are investigated. Comparative experimental results demonstrate that the irreversible failure occurs in the depletion-mode (D-mode) GaN HEMT, driven by high surge current and its resultant increasing surge voltage. Further physical failure analysis localized the failure point around the drain electrode. Moreover, by mixed-mode simulations, it is validated that joule heat accumulates rapidly around the drain electrode and eventually causes the device to burn out. Besides, it is proved that better heat dissipation for drain metal pads of devices improves the surge current capability, which provides an easy-to implement optimization for Cascode GaN HEMTs when operating in the third quadrant.